So the Miata I recently bought (which is now nicknamed Bucket) needed a new rear window fitted due to the glass one delaminating and falling out. The process to make your own is pretty simple. You'll need clear Marine Vinyl, Loctite PL Marine Fast Cure, scissors, magnets and a caulking gun.
1. First lay the vinyl over the back window opening, and trim the vinyl to shape, making sure to leave 2-3 inches extra on each side.
1a. In my case, the canvas folded over the window frame and I was no longer using that so I cut off the excess since it was covered in excess adhesive
2. Open the doors, go inside the miata and clean the inside the top for a good seal.
3. Grab the caulk gun, cut the tip off the marine sealant and lay down 2 beads of sealant around the opening
4. Take the vinyl and apply it to the beads of sealant, making sure to leave a little bit of slack on the vinyl to prevent ripping or tearing, hence the 2-3 inches of excess.
5. In my case I used the old window frame since it's metal, but you can also use flat scrap metal on the inside of the top and magnets on the outside of the top to keep pressure on the sealant while it cures
6. Wait 24 hours for sealant to cure, then remove magnets and metal.
Miata is going to be parked outside this weekend to test the rain and heat tolerance on the marine sealant but it should be alright.
Going to attach photos in a separate comment as I keep trying on my phone and it doesn't work.
